THe benchmark I gave is what I feel is reasonable:But the point you bring up, the "you as DM want" POV, is very much a relevant potential issue.
Do you as GM feel obliged to work reliable access to costly material components into the mix of situations and circumstances? What is the longest period (game time or levels) a player should have to be without access to the components for spells? Do you handle some spells differently - diamonds for revivify, resurrection vs diamonds for chromatic orb, or 50 gp diamonds vs 100gp crafted horns? (Not defined by RAW so obviously an "in your games")
* a character with resources working for a week or two (travelling to a better town; finding a mine, or whatever) should be able to find access to any moderate material component (not necessarily a 1000gp gem, but a 100gp one no problem).
* a player making a design choice should be able with effort to accomplish that outcome within a level. (And so, if a character wants to retrain a skill, I say don't use it for the current level, and the next time you level up, you can have something different.)
Because a player should be able to have the character they want. If I don't want them to have a familiar (hypothetically), I should just say that outright, and not make it an in-game ordeal, when it wouldn't be for another character at the same level in another circumstance.
Now at the same time, a character might learn the spell and not work to get the material components. They shouldn't fall into his lap, but they should be reasonably available in the game world.